Oil spillages constitute a severe pollution threat. Much effort has been devoted to developing methods capable of collecting oil spilt into water or otherwise neutralising the threat posed by such spilled oil. The use of detergents to disperse spilt oil is unsatisfactory in that the detergents themselves are an environmental hazard and the oil frequently reappears after it has apparently been dispersed. Oil containment booms have been proposed to prevent the spreading or drifting of spilt oil whilst collection of the oil can be carried out. Such booms however are too expensive to be used to contain very large spillages.
Numerous methods of collecting spilt oil have been proposed. Some employ collection media which absorb oil and are disposed of once the oil has been absorbed. Some employ a collection medium from which the oil may be removed so that the collection medium may be reused.
It is known that certain plant materials and in particular straw are capable of collecting oil. Attempts have been made in the past to collect oil from water by floating bales of straw in the water. Use of individual bales in this manner is however impractical on a large scale in view of difficulties of handling the individual bales and in view of the tendency of the bales to break up once in the water so that the oil saturated straw cannot itself be collected easily.
I have now developed a product employing plant material such as straw for its oil collecting properties which avoids the disadvantages described above. The present invention is however applicable not only to plant material packaged for use in collecting oil but also to the packaging of plant material for storage and for use in many other situations and is applicable also to the handling of plant material not suitable for collecting oil eg. for use as fodder.
British Patent Specification No. 1352741 describes a mat of cellulose fibres treated to be water repellant, encased in wire netting and rolled up for storage ready for use in absorbing oil as a contaminant on land or water. It condemns the previously known use of loose straw as an absorbent as being largely ineffective.
U.S. Pat. No. 3,617,566 describes the use of straw as a carrier for atactic polypropylene to be encased in a net bag to absorb oil and refers to previous use of loose straw as an absorbent as being ineffective.
It has also been proposed elsewhere to encase other plant derived materials (e.g. bark in British Patent Specification No. 1210690) in net for oil absorbing.
Such methods have not been found sufficiently effective or economical to gain wide acceptance. With regard to U.S. Pat. No. 3,617,566, straw is light and voluminous making it expensive to transport for treatment. No machinery is described for packing the straw efficiently into net bags. Methods and apparatus are wanted for encasing straw or like plant stem materials which can be used in proximity to where the straw is grown or even in the very field in which it is grown so as to reduce transport costs. Furthermore, if straw is simply encased in net bags, the straw will tend to clump unevenly in the net bags encasing it when these are deployed for oil absorption on land or on water.
I have found that plant stem material such as straw in the form of a mat encased in a water permeable encasing material such as net is a very useful absorbent for oil in many situations including for floating at sea and for pegging out on the shore to catch oil as it washes ashore. I have found further found that by attaching opposed layers of the encasing material through the mat the clumping of the straw in use is substantially prevented, thus enhancing the utility of the product.